Hi @fishyaker ,
I am not sure what your sequence of events is, but I had this sort of trouble when I accidentally installed a ZFS filesystem on a disk, then wiped it with Gparted and went back to a normal partitioning with ext4 filesystems.
So question, did you use ZFS , then change back to some other filesystem?
The problem is ZFS leaves trace of itself right at the beginning of the disk, in the MBR region, and these traces interfere with grub booting.
There was a post on the issue called .
Wipe ZFS signatures from a disk
If you think it is relevant to your issue, you should read it.
You can check if there are any ZFS residues by doing
# wipefs /dev/sda
Be careful using wipefs… it is as dangerous as it sounds. The above is safe, it is just a query.
I hope this is not your issue, because it is a beast to get rid of, but there is a method… see the post
Regards
Neville